The Hockaday Museum of Art in Kalispell is featuring an exhibit of photographs that chronicle the century-long recession of glaciers in Glacier National Park.

The exhibit - "Losing a Legacy: A Photographic Story of Disappearing Glaciers' - is on display through April 10.

The exhibit was developed by U.S. Geological Survey staffers based in Glacier.

It is based on 'repeat photography," a method by which modern images are taken from the exact same locations as historic photographs.

"The glacier images reveal dramatic glacial decline over a century and are in line with predictions that all of the glaciers in Glacier National Park will disappear by 2030," a USGS press release states.

The photography concept was inspired by the discovery of historical park images dating back as far as 1861, when the first photos were taken of the boundary markers between Canada and the United States.

Over time, numerous park images were taken for purposes ranging from tourism promotion to scientific research.

"While our original intent was to use the photography for science, through time we've found that these photographs do more than document, they inspire," said Lisa McKeon, who has spent hours in the park backcountry taking repeat photographs of remaining glaciers.

USGS ecologist Dan Fagre started the project in 1997. Since the onset of the project, more than 70 photographs of 19 different glaciers have been repeated in the park.

While all of the glaciers are shrinking, 13 have shown significant recession. Some of the more intensely studied glaciers have been found to be just one third of their estimated size at the end of the last cold period in 1850. And only 25 of the 150 named glaciers that were present in 1850 remain today.

Examples of the repeat photography project can be viewed online at the USGS Web site:

http://nrmsc.usgs.gov/repeatphoto/overview.htm